1. Field of the Invention
The present invention concerns a variable size folding machine for a printing machine having a plurality of plate cylinder sizes such as a rotary gravure press and it relates to a cross perforater for forming a lateral perforated line to a print paper after printing.
2. Description of the Related Art
Generally, a print paper continuously printed in a printing machine is fed from an upper folder to the inside of a folding machine, in which the printed paper is properly applied with longitudinal or lateral cutting and folding and then discharged as signatures from the folding machine. In this case, a plurality of plate cylinders having different sizes (plate cylinder diameter) are sometimes used in a printing machine for applying printing on the print paper and, correspondingly, a variable size folding machine capable of folding different sizes of signatures is used also as the folding machine disposed at the downstream of the printing machine.
FIG. 8 shows a portion of a variable size folding machine 900 as an example of such a variable size folding machine in the prior art.
In FIG. 8, the variable size folding machine 900 is adapted to introduce a print paper 901 printed continuously by a printing machine such as a rotary printing press at the upstream, from an upper folder not illustrated, which is then cut and put to lateral folding and chopper folding (longitudinal folding) and discharged as folded sections 902. The variable size folding machine 900 comprises nipping rollers 903, 904 and 905, 906, a male cutting cylinder 910 and a female cutting cylinder 911, a signature acceleration conveyor 920, an gripper & tucking cylinder 930, a jaw cylinder 940, an upper slow-down cylinder 950 and a lower slow-down cylinder 951 and choppers 960, 961, which are arranged from the upstream in the delivering direction of the print paper 901 or the signature 902, that is, from the side of the upper folder.
In such a variable size folding machine 900, the print paper 901 delivered continuously from the printing machine is introduced from the upper folder not illustrated, delivered to the male cutting cylinder 910 and the female cutting cylinder 911 while being held by the nipping rollers 903, 904 and 905, 906, in which it is cut into signatures 902 of a predetermined size. The cut signatures 902 are accelerated, being put between belts 921 and 922 from both sides in the signature acceleration conveyor 920 and then handed to the gripper & tucking cylinder 930.
The gripper & tucking cylinder 930 has chuck fingers 932, and the cut and accelerated signature 902 is gripped at the top end by the chuck finger 932 and sent to the jaw cylinder 940. Further, the gripper & tucking cylinder 930 has insertion plates 931 situated alternately with the chuck fingers 932. The insertion plate 931 is inserted into the direction of the jaw cylinder 940 at a portion of contact between the jaw cylinder 940 and the gripper & tucking cylinder 930, by which the folded section 902 is caught at its lateral folding position (about at a mid portion) by a chuck plate 941 and a chuck jaw 942 of the jaw cylinder 940 and then sent to the upper and the lower slow-down cylinders 950 and 951.
Belts 952 and 953 are wound around (as shown by dotted chains in FIG. 8) the upper and the lower slow-down cylinders 950 and 951, and belts 954 and 955 are wound around (as shows by dotted lines in FIG. 8) below each of the slow-down cylinders 950 and 951 so as to oppose the above-mentioned belts 952 and 953 respectively.
Each of the slow-down cylinders 950 and 951 has a chuck finger 957 that catches the signature 902 sent from the jaw cylinder 940 at a laterally folded position and the signatures 902 are alternately distributed into upper and lower portions by the chuck fingers 57 of the upper and the lower slow-down cylinders 950 and 951.
Then, the signatures 902 distributed into the upper and lower portions are delivered, in the laterally folded state, while being put between the belts 952 and 954 and the belts 953 and 955 to each of choppers 960 and 961 at the downstream, in which they are put to chopper folding and discharged by way of a conveyor or the like.
In such a variable size folding machine 900, since the delivery speed of the print paper 901 after cutting, that is, the delivery speed of the signatures 902 after delivered from the signature acceleration conveyor 920 is set to higher than a surface circumferential speed of the plate cylinder of the maximum size among a plurality of plate cylinder sizes in the printing machine at the upstream, that is, since it is set to greater than the maximum delivery speed of the print paper 901 in a continuous state before cutting, it can cope with all sorts of plate cylinder sizes, that is, all of the sizes of the signatures 902.
However, in such an existent variable size folding machine 902, since the print paper 901 is cut in the male cutting cylinder 910 and the female cutting cylinder 911, then accelerated by the signature acceleration conveyor 920 and laterally folded being gripped by each of the cylinders on and after the gripper & tucking cylinder 930, there has been a problem that an accuracy for lateral folding is not satisfactory as compared with a case of cutting the print paper after gripping by the chuck fingers in the existent fixed type folding machine.
That is, in a process where the print paper 901 is accelerated after cutting and then gripped, there has been a problem that the signature 902, can not be gripped stably at predetermined positions upon gripping by the chuck finger 932 of the gripper & tucking cylinder 930, gripping by the chuck plate 941 and the chuck jaw 942 of the jaw cylinder 940 or gripping by the chuck finger 957 of each of the slow-down cylinders 950 and 951.
Further, such a variable size folding machine 900 has involved a problem of requiring much time and labour for adjusting the phase between each of the cylinders so that the lateral folding is applied at a predetermined position of the signature 302, in a case if the type of the print paper 901 is changed.
Further, in a case of printing books or publication matters, chopper folding (longitudinal folding) is further applied after the lateral folding as done in each of the choppers 960 and 961 in the variable size folding machine 900. However, this has caused a problem that fold wrinkles 970 which are referred to "gutter wrinkles" are liable to occur at a portion inside the chopper fold (portion A in the figure) as shown in FIG. 7, particularly, in a case where the signature 902 is folded into 16 or more pages.
In view of the problem for the accuracy in lateral folding or a problem of "gutter wrinkles" in such a variable size folding machine 900, a counter measure may be considered to form a lateral perforated line at a position of a lateral score before lateral folding.
That is, when a lateral perforated line 971 is formed previously as shown in FIG. 10, stable lateral folding (portion B in the figure) can be applied at a predetermined position of the signature 902, and occurrence of "gutter wrinkles can be eliminated because air in the signature 902 escapes through apertures of the lateral perforated line 971 upon chopper folding.
However, as an actual problem, the existent variable size folding machine 900 can not be provided with a cross perforater for forming the above-mentioned lateral perforated line by the reasons described below.
That is, the print paper (web) 901 printed by a plate cylinder of the printing machine at the upstream and sent in the continuous state therefrom is delivered at a speed equal with the surface circumferential speed of the plate cylinder of the printing machine. However, since the printing machine at the upstream of the variable size folding machine 900 has a plurality of plate cylinder sizes (plate cylinder diameter), the surface circumferential speed of the plate cylinder varies in accordance therewith and, thus, the delivering speed of the print paper 901 varies.
In this case, for fabricating the lateral perforated line 971 to the print paper 901 in the form of the web, the surface circumferential speed of the lateral line perforation cylinder and the leteral line female perforation cylinder of the cross perforater for forming the lateral perforated line 971 has to be aligned with the surface circumferential speed of the plate cylinder of the printing machine, that is, the delivering speed of the print paper 901 in the form of the web. If the delivering speed of the print paper 901 does not match the surface circumferential speed of the lateral line perforation cylinder and the leteral line female perforation cylinder, the lateral perforated line 971 is drifted in the delivering direction of the print paper 901, as well as the printing quality is deteriorated due to friction between the surface of the print paper 901 and the surface of the lateral line perforation cylinder and the leteral line female perforation cylinder. Accordingly, if the delivering speed of the print paper 901 varies due to the presence of a plurality of plate cylinder sizes, the surface circumferential speed of the lateral line perforation cylinder and the leteral line female perforation cylinder of the cross perforater have also to be varied in accordance therewith.
By the way, in order to change the surface circumferential speed by using identical lateral line perforation cylinder and leteral line female perforation cylinder, namely, without changing the diameter of such cylinders, it may be considered to change the rotational speed (number of rotation) of such cylinders, for example, by using a speed changing device.
However, since the rotational speed (number of rotation) of the lateral line perforation cylinder and the leteral line female perforation cylinder of the cross perforater and the rotational speed (number of rotation) of the plate cylinder of the printing machine is set to a constant rotational ratio, the rotational speed of the lateral line perforation cylinder and the leteral line female perforation cylinder can not be changed by using the speed changing device or the like and, accordingly, the surface circumferential speed of the lateral line perforation cylinder and the leteral line female perforation cylinder can not be changed.
The rotational speed of the lateral line perforation cylinder and the leteral line female perforation cylinder and the rotational speed of the plate cylinder of the printing machine have to be kept at a constant rotational ratio, because the lateral perforated line 971 has always to be fabricated at a predetermined position to a signature 902 and, accordingly, the number of sheets printed per unit time by the plate cylinder of the printing machine (corresponding to the signature 902) and the number of sheets per unit time applied with the lateral perforated line 971 by the lateral line perforation cylinder and the leteral line female perforation cylinder (corresponding to the folded section 902) have to be aligned.
If the rotational speed of the lateral line perforation cylinder and the leteral line female perforation cylinder were changed by using a speed changing device or the like, since the constant rotational ratio described above can not be maintained, the lateral perforated line 971 can not be applied always at the predetermined position of the signature 902. This results in such a disadvantage that the position for the lateral perforated line 971 gradually displaces relative to the signature 902 or lateral perforated lines 971 are formed at a plurality of portions to one signature 902, or a signature 902 not having the lateral perforated line 971 will result.
With the reasons as described above, the variable size folding machine 900 could not be provided with the cross perforater so far.
An object of the present invention is to provide a variable size folding machine capable of improving an accuracy of the lateral folding of a signature and capable in preventing occurrence of folding wrinkles.